Now I know this may sound a little contreversial, but surely the best source for ideas for the Shuttle replacement, or CEV, or what ever they're calling it now, would be to look at not only the aeorspace industry, but also some of the many authors who make they're living from the Space industry.
I've lost count of the times that I've read a book where the Author has obviously done his research, and put forward very valid ideas that NASA would be stupid to ignore.
For Example a Shuttle replacement propossed in the Books "Origin", "Time", "Space" and "Phase space" by Stephen Baxter uses the equivilent of off the shelf parts.
A Shuttle tank with 4 Shuttle motors mounted underneath, 2-4 Solid boosters (depending on Payload weight) and the Cargo module/spaceplane mounted on the nose. Voila, no off axis Thrust problems, no putting crew and cargo dangerously astride the fuel tank, and all using parts that are already being produced for the current Shuttle program.
It would also make the Stack more efficeint as it could be used for both unmanned cargo runs as well as CEV launches.
Of course this could then be upgraded to carry heavier loads higher and further by using new hybrid fuels, more solid boosters, or many other things I probably haven't thought of.
Plus there's the added bonus that as it's based on the Shuttle Stack, pads 39a and 39b at Kennedy wouldn't need much (if any) alteration.

Plus there's the added bonus that as it's based on the Shuttle Stack, pads 39a and 39b at Kennedy wouldn't need much (if any) alteration.

Of course, the resemblance to Shuttle works both ways. The bad part is that it will share another attribute with Shuttle, called expense. The shuttle currently costs $4 billion a year to fly. Obviously, without the orbiter and with fewer flights per year, costs would decrease somewhat, but it would still be in the billions. The Saturn V seems cheaper.

My personal choice for a heavy launch vehicle would be an upgrade of the Delta IV Heavy. By introducing new materials and improved engines, you could get payload capacity almost equal to a Shuttle-C design. And it would be a lot cheaper, presumably, since the estimated price of a (normal) Delta IV Heavy is $250 million. Even if the price doubled, it's still a good deal.

Plus, the Delta IVH has no solid motors, while the Shuttle-C would. And wasn't it Wernher von Braun who said solids have no place on a manned vehicle?

In any event, these sorts of decisions are in the far future. Under the Bush plan, we aren't going to the moon for a decade, so we have plenty of time to debate different launch vehicles.

Believe it or not, the Saturn V cost less to operate than the Space Shuttle does now -- and that's counting inflation. This is because something over 40% of the mass of the Orbiter has to be replaced after each mission (I think it's more like 70%, but I'm not sure) -- everything from the wiring to the ceramic tiles to the tires, all stripped, trashed, and replaced.

One of the primary problems with both of the launch vehicles mentioned above is the fact that they are one-way, absolutely cannnot return to Earth in any meaningful way other than as a fireball, and are therefore inefficient. The only way a space transport company will truly succeed is if it uses a vehicle that is almost completely reusable -- hence the X-Prize restriction on only 10% of the vehicle's non-propellant mass being replaceable.

Plus, the Delta IVH has no solid motors, while the Shuttle-C would. And wasn't it Wernher von Braun who said solids have no place on a manned vehicle?

The Shuttle-C would not carry people only cargo.

For the cost I have not found any cost estimates for launching the Shuttle-C so comparing the Shuttle-C to Saturn V would be hard because the Saturn V you throw away every thing but with the Shuttle-C you do get back the Solid boosters and the shuttle motor and electronics. Also with the Shuttle-C you don’t have the most maintenance intense part of the shuttle “the orbiter” and you can use all the weight savings for the cargo. But NASA will need more powerful rockets down the road.

Precisley. The greatest complaint ex-NASA workers have is about the "if it was designed here it wasn't a good idea". This has plauged NASA since its inception, from Man High through to the well-known difficulty in getting LOR pushed through for apollo.

Whether it continues... Well we have a whole new generation of engineers and management who haven't really built anything yet so we don't know. The current hang-up is a love of computer simulations.

As of new ideas? There are plenty of new ideas even coming from non-fiction authors. The best bit is some of these are actually filtering in. Robert Zubrin has managed to get the threads of his Mars-Direct plan into NASA although it still morphed a whole lot. But it is a sign that they are willing to listen.